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A Stripline Antenna for Radiated Immunity Testing

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A Stripline Antenna for Radiated Immunity Testing A STRIPLINE ANTENNA FOR RADIATED IMMUNITY TESTING Franciscus Jozua van Dam EWI TELECOMMUNICATION ENGINEERING EXAMINATION COMMITTEE Prof. Dr. Ir. ing. F.B.J. Leferink Dr. Ir. M.J. Bentum Ir. J. Schipper 27-10-2011 The use of different radiating structures for radiated susceptibility test Electromagnetic Compatibility (EMC)is a field of ongoing research. Especially with relative long wave lengths for frequencies between 2-30 MHz in the confined space of an anechoic chamber which is used to test for radiated susceptibility it is not easy to generate a strong and uniform electric field for large pieces of equipment. The main question in this research was to see whether it was possible to build a large stripline antenna for the testing of pieces of equipment of roughly 2.0m high, combined with a high field strength of 200 V/m when using a 2.5kW amplifier. Small stripline antennas have been internationally standardized for EMC testing for small components or wire bundles in the automotive industry in the ISO 11452-5. In this research available literature has been studied and stripline antennas have been simulated with computational electromagnetics software. Furthermore experiments with scale models in an anechoic chamber have been performed. Stripline antenna impedance depends heavily on the width/height. In order to keep the stripline antenna physically realizable with in the anechoic chamber, stripline antennas for input impedances greater than 50Ω have been simulated and tested in practice. Impedances of 200Ω and 100Ω have been transformed to 50Ω using ferrite core based unbalanced to unbalanced transmission line transformers of the Ruthroff type. Results of these experiments have led to a possible solution in the form of a wire stripline antenna with an impedance of 100Ω. The S11 parameter is -10 dB or better over a frequency range from 2 to 30 MHz. iii iv Het gebruik van verschillende structuren voor het doen van testen met betrekking tot de stralingsgevoeligheid binnen de Elektromagnetische Compatibiliteit is een veld van continu onderzoek. De lange golflengten voor de lage frequenties in het gebied van 2 tot 30 MHz in de beperkte ruimte van een semi anechoische ruimte welke gebruikt wordt voor het doen van stralingsgevoeligheid maken het lastig om een sterk en uniform elektrisch veld te genereren. De hoofdvraag voor dit onderzoek was of het mogelijk is om een grote stripline antenne te bouwen voor apparatuur met een hoogte van 2.0m in combinatie met een veldsterkte van 200 V/m waarbij een 2.5 kW versterker wordt gebruikt. Kleine stripline antennes zijn internationaal gestandaardiseerd voor het testen van kleine componenten of draadbundels in de auto-industrie in de ISO 11452-5 standaard. In dit onderzoek is de aanwezige literatuur bestudeerd en zijn stripline antennes gesimuleerd met speciale software welke geschikt is voor het berekenen van elektromagnetische velden. Verder zijn experimenten gedaan met schaalmodellen in de anechoische ruimte. Gezien de afhankelijkheid van de hoogte en breedte verhoudingen voor de antenne impedantie zijn er testen gedaan met impedanties van 50Ω, 100 Ω en 200 Ω welke zijn gesimuleerd en getest in de praktijk. Impedanties van 200Ω en 100Ω zijn getransformeerd naar een impedantie van 50Ω doormiddel van ongebalanceerde transmissielijn transformatoren met ferriet kernen van het Ruthroff type. Resultaten van deze experimenten hebben geleid tot een mogelijke oplossing in de vorm van een stripline antenne met een impedantie van 100Ω of 200Ω. De reflectiecoëfficiënt van de ontworpen 100Ω stripline antenne is beter of gelijk aan -10dB in het frequentiegebied van 2 tot 30 MHz. v vi SUMMARY ......................................................................................................................................... III SAMENVATTING ................................................................................................................................ V TABLE OF CONTENTS ........................................................................................................................ VII TABLE OF FIGURES .............................................................................................................................IX LIST OF ABBREVIATIONS................................................................................................................... XIII CHAPTER 1 INTRODUCTION ............................................................................................................ 1 1.1 STRIPLINE ANTENNAS .......................................................................................................................... 1 1.2 ABOUT ELECTROMAGNETIC COMPATIBILITY .............................................................................................. 1 1.3 THE NEED FOR RADIATED SUSCEPTIBILITY TESTING ..................................................................................... 3 1.4 REQUIREMENTS FOR THE GENERATED ELECTRIC FIELD ................................................................................. 3 1.5 STRUCTURE OF THIS THESIS ................................................................................................................... 5 CHAPTER 2 ELECTROMAGNETIC WAVES AND TRANSMISSION LINES ................................................ 7 2.1 TM AND TE WAVES ............................................................................................................................ 7 2.2 TRANSMISSION LINE PARAMETERS AND TEM PROPAGATION ...................................................................... 7 2.3 SCATTERING PARAMETERS AND THE REFLECTION COEFFICIENT. ................................................................... 10 2.3.1 Limiting the S11 and S21 coefficients ................................................................................. 11 2.4 TEM CELLS ..................................................................................................................................... 12 2.4.1 Advantages of a TEM cell ................................................................................................... 13 2.4.2 Disadvantages of a TEM cell .............................................................................................. 13 2.5 TRI-PLATES ...................................................................................................................................... 14 CHAPTER 3 STRIPLINE ANTENNA PROPERTIES FROM THE LITERATURE........................................... 15 3.1 MICROSTRIP TRANSMISSION LINES ....................................................................................................... 15 3.2 STRIPLINE ANTENNA PROPERTIES ......................................................................................................... 16 3.2.1 Electric Field Strength ........................................................................................................ 16 3.2.2 Stripline antenna Impedance ............................................................................................. 17 CHAPTER 4 IMPEDANCE MATCHING.............................................................................................. 21 4.1 LUMPED ELEMENT MATCHING ............................................................................................................. 21 4.2 BALUNS AND TRANSMISSION LINE TRANSFORMERS ON FERRITE AND IRON POWDER CORES .............................. 22 2 4.2.1 Guanella 1:1 and 1:n balun Transmission Line Transformers ........................................... 22 4.2.2 Ruthroff ununs 1:4, 1:2.25 and 1:2 .................................................................................... 23 4.2.3 Ferrite and Iron Powder cores ............................................................................................ 24 4.3 ANTENNA TUNERS ............................................................................................................................ 26 CHAPTER 5 COMPUTATIONAL ELECTROMAGNETICS, PACKAGES AND PRINCIPLES ......................... 27 5.1 THE FINITE ELEMENT METHOD AND THE MODELS IN HFSS ........................................................................ 27 5.1.1 The solid model in HFSS ...................................................................................................... 28 5.2 THE METHOD OF MOMENTS AND THE SLA MODELS IN FEKO .................................................................... 29 5.2.1 A solid plate model in FEKO ............................................................................................... 30 5.3 STRIPLINE ANTENNA RESULTS IN COMPUTATIONAL ELECTROMAGNETICS ...................................................... 32 5.3.1 The equipment under the stripline antenna ....................................................................... 33 5.3.2 Angles of the feeding part of the SLA ................................................................................. 34 CHAPTER 6 A 50Ω SLA REALIZATION AND MEASUREMENTS .......................................................... 37 6.1 AN ALUMINIUM FOIL 50Ω SLA ........................................................................................................... 37 CHAPTER 7 A 200Ω SLA WITH TWO 1:4 UNUNS, 50:200Ω .............................................................. 45 7.1 A GUANELLA 1:1 BALUN TO SELECT CORES ............................................................................................ 45 7.2 A 1:4 RUTHROFF UNUN ....................................................................................................................
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